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22 Chemistry of the Nonmetals Solutions to Exercises (b) (aq) + S(s) + (aq) + + (or (aq) + S(s) + (aq) + + (c) + + 2NO(g) + + (aq) (d) N₂H₄(g) + 2NF₃(g) + 4HF(g) (e) + 3N₂H₄(aq) + + + 22.57 Analyze/Plan. Follow the method for writing balanced half-reactions given in Section 20.2 and Sample Exercises 20.2 and 20.3 Solve. (a) + (aq) + (aq) + 2e⁻, = 0.96 V (b) + + (aq) + 2e⁻, = 1.77 V 22.58 (a) + 4H+ + NO(g) + (b) NO₂(g) + (aq) + 22.59 Analyze/Plan. Follow the rules for assigning oxidation numbers in Section 4.4 and the logic in Sample Exercise 4.8. Solve. (a) +3 (b) H4P2O7, +5 (c) SbCl₃, +3 (d) (e) +5 (f) +5 22.60 (a) +5 (b) +3 (c) (d) Ca(H₂PO₄)₂,+5 (e) -3 (f) GaAs, -3 22.61 Analyze/Plan. Consider the structures of the compounds of interest when explaining the observations. Solve. (a) Phosphorus is a larger atom and can more easily accommodate five surrounding atoms and an expanded octet of electrons than nitrogen can. Also, P has energetically "available" 3d orbitals which participate in the bonding, but nitrogen does not. (b) Only one of the three hydrogens in is bonded to oxygen. The other two are bonded directly to phosphorus and are not easily ionized because the P-H bond is not very polar. (c) PH₃ is a weaker base than H2O (PH₄⁺ is a stronger acid than Any attempt to add to PH₃ in the presence of merely causes protonation of (d) Refer to the structures of white and red phosphorus in Figure 22.27. White phosphorus consists of molecules, with P-P-P bond angles of 60°. Each P atom has four VSEPR pairs of electrons, so the predicted electron pair geometry is tetrahedral and the preferred bond angle is 109°. Because of the severely strained bond angles in molecules, white phosphorus is highly reactive. Red phosphorus is a chain of groups of four P atoms. It has fewer severely strained P-P-P bond angles and is less reactive than white phosphorus. 22.62 (a) Only two of the hydrogens in are bound to oxygen. The third is attached directly to phosphorus, and not readily ionized, because the H-P bond is not very polar. 680